Until the first quarter of the 20th century, the Milky Way galaxy was all we knew of the universe. Static and eternal, it consisted of a 100 billion stars and a multitude of questions. Then came a burst of technology and research, which has lasted six decades and is still in progress. We know that 15 billion years ago the universe exploded from its tiny seed, leaving scattered through empty space billions of galaxies filled with such exotica as neutron stars, black holes, pulsars, quasars, white dwarfs and red giants. The hiss of cosmic microwave radiation remains as testimony to the Big Bang of creation.